Bitumen composition

ABSTRACT

The present invention provides a bitumen composition including:—(i) from 0.1 to 25% wt of an elastomer, (ii) from 0.1 to 40% wt of a solvent, (iii) from 30 to 99% wt of a bitumen, (iv) from 0.1 to 30% wt of a lithium salt of a C 10 -C 40  fatty acid or hydroxy fatty acid, and optionally (v) from 0 to 70% wt of a filler, all weights based on total bitumen composition, wherein the solvent is of general formula (I),  
                 
 
wherein R 1  represents a hydrogen atom or a hydrocarbyl group having from 1 to 6 carbon atoms, R 2  represents a hydrocarbyl group having from 1 to 6 carbon atoms, and the sum of the carbon atoms in R 1  and R 2  is from 5 to 7; a process of preparing said bitumen composition and the use of the composition as a cold-applicable adhesive.

The present invention relates to a bitumen composition, a process ofpreparing a bitumen composition, and the use of a bitumen composition asan adhesive.

BACKGROUND OF THE INVENTION

Bitumen is a versatile material that is widely used in civilengineering. One use of bitumen is as an adhesive for repairing cracksin buildings and road surfaces, and as a joint sealant. When used as anadhesive, it is generally necessary to heat the bitumen to a temperaturewhere it becomes workable before it can be applied. However, for certainapplications this is inconvenient and bitumen compositions have beendeveloped which are cold-applicable, i.e. they may be applied as anadhesive without the need for heating. One such composition is describedin EP-A 37136.

The compositions of EP-A 37136 are cold-applicable adhesives thatcomprise bitumen, an elastomer, and a lithium salt of a fatty acid. Thelithium salt acts as a thixotropic agent, causing the composition toharden after application. The compositions have the ability to bond tomany substrates in cold and damp conditions and are widely used assealants on metal, concrete and brickwork; in the roofing industry; andin hydraulic applications, for example as sealants for canal linings orwaterproofing cement concrete dams.

To facilitate application, the compositions of EP-A 37136 may furthercomprise an aromatic hydrocarbon solvent (e.g. benzene, toluene, xyleneetc) or a halogenated hydrocarbon solvent (e.g. dichloromethane or1,1,1,-trichloroethane). These solvents evaporate after application,causing the composition to harden or cure.

To date, the only solvents considered suitable for use incold-applicable compositions such as those described in EP-A 37136 arearomatic hydrocarbon solvents or halogenated solvents;1,1,1,-trichloroethane being especially preferred. However, in recentyears it has been found that aromatic hydrocarbon and halogenatedsolvents are harmful to the environment and may have detrimental effectson human health. Therefore, it would be advantageous if there was ameans of replacing these solvents in cold-applicable bituminousadhesives.

SUMMARY OF THE INVENTION

It has now surprisingly been found that a bitumen composition comprisingan ester-based solvent has excellent properties for use as acold-applicable adhesive. As well as having properties approaching orequal to those of compositions comprising halogenated or aromatichydrocarbon solvents, the compositions are an improvement on existingformulations in that the ester-based solvents are more desirable from anenvironmental perspective and do not pose a threat to human health.

Accordingly, the present invention provides a bitumen compositioncomprising:—

-   -   (i) from 0.1 to 25% wt of an elastomer,    -   (ii) from 0.1 to 40% wt of a solvent,    -   (iii) from 30 to 99% wt of a bitumen,    -   (iv) from 0.1 to 30% wt of a lithium salt of a C₁₀-C₄₀ fatty        acid or hydroxy fatty acid, and optionally    -   (v) from 0 to 70% wt of a filler, all weights based on total        bitumen composition,        wherein the solvent is of general formula (I):—        wherein R¹ represents a hydrogen atom or a hydrocarbyl group        having from 1 to 6 carbon atoms, R² represents a hydrocarbyl        group having from 1 to 6 carbon atoms, and the sum of the carbon        atoms in R¹ and R² is from 5 to 7.

DETAILED DESCRIPTION OF THE INVENTION

The bitumen composition of the present invention comprises from 0.1 to40% wt of a solvent of general formula (I). The amount of solvent mayvary depending on the manner in which the bitumen composition is to beapplied. For example, where the composition is applied using a spatula,hand-held cartridge or application-gun for precise application, theamount of solvent may conveniently be in the range of from 5 to 15% wt,preferably 9 to 12% wt, based on total bitumen composition. However,when the bitumen composition is to be applied as a spray to treat alarge surface area, the amount of solvent may conveniently be in therange of from 15 to 30% wt, based on total composition.

Preferably, in general formula (I) R¹ and R² each independentlyrepresent a hydrocarbyl group having from 1 to 6 carbon atoms. Thehydrocarbyl groups of general formula (I) are unsubstituted. Thehydrocarbyl groups may be straight or branched chain, saturated orunsaturated; preferred hydrocarbyl groups being alkyl or alkenyl groupshaving from 1 to 6 carbon atoms, more preferably alkyl groups havingfrom 2 to 4 carbon atoms, e.g. ethyl, propyl, and butyl groups.Particularly preferred are n-alkyl groups having from 2 to 4 carbonatoms.

In general formula (I), the sum of the carbon atoms in R¹ and R² is from5 to 7. This is because when the sum of the carbon atoms is greater than7, the curing times of the composition are too slow; and when the sum ofthe carbon atoms is less than 5, the solvents are too flammable to beused safely in the compositions. Preferably, the sum of the carbon atomsin R¹ and R² is 6.

When the bitumen composition of the present invention is applied, thesolvent of general formula (I) will evaporate and the composition willcure. The time taken for the composition to cure will vary depending onthe thickness of composition applied, however, curing times willconveniently be in the range of from 7 to 60 days, preferably from 10 to30 days. In this regard it is preferred that the solvent of generalformula (I) has a boiling point of from 110 to 180° C., more preferablyfrom 120 to 160° C.

In a preferred embodiment of the present invention the bitumencomposition comprises a solvent of general formula (I) wherein R¹ and R²each independently represent an alkyl group having from 2 to 4 carbonatoms and the sum of the carbon atoms in R¹ and R² is 6. Examples ofsolvents that may very conveniently be used in accordance with thisembodiment include ethyl valerate, ethyl isovalerate, ethyl2-methylbutyrate, n-propyl butyrate, isopropyl butyrate, n-butylpropionate, and isobutyl propionate.

The solvents of general formula (I) are esters that are commerciallyavailable and/or readily prepared by known chemistry. A solvent ofgeneral formula (I) which gives very good results when used in thepresent invention is n-butyl propionate, which can be obtained from theEastman Chemical Company or the Dow Chemical Company (boiling point 145°C.).

The bitumen (iii) of the present invention may be a naturally occurringbitumen or a bitumen derived from a mineral oil, e.g. a cracked residue,or a blend of various bitumen types.

Examples of bitumen that may be conveniently used in the presentinvention include distillation or “straight run” bitumen, precipitationbitumen (e.g. propane bitumen), and oxidised or air-blown bitumen. Otherbitumen that may be used include mixtures of one or more of thesebitumen with extenders such as petroleum extracts, distillates orresidues, and oils. Preferably, the bitumen is a distillation or“straight run” bitumen, optionally containing an extender.

Preferably, the bitumen (iii) has a penetration from 100 to 300 dmm,more preferably from 140 to 260 dmm (measured at 25° C. according to EN1426). The softening point of the bitumen is preferably from 30 to 50°C., more preferably 34 to 43° C. (measured according to EN 1427).

The amount of bitumen in the bitumen compositions is preferably from 30to 75% wt, more preferably 30 to 60% wt, and most preferably 35 to 50%wt, based on total bitumen composition.

The bitumen composition of the present invention comprises from 0.1 to25% wt of an elastomer (i). Preferably, the amount of elastomer is from0.2 to 10% wt, more preferably 0.5 to 6% wt and most preferably 1 to 3%wt, based on total bitumen composition.

A wide variety of elastomers may be used in the bitumen composition ofthe present invention. Examples of elastomers that may be convenientlyused include polyesters, polyacrylates, polysulphides, polysisliconesand polyesteramides that show elastomer behaviour.

A class of elastomer that may very conveniently be used in accordancewith the present invention are elastomers based upon polymers of dienes,such as butadiene or isoprene, or copolymers of such dienes with a vinylaromatic compound such as styrene.

Accordingly, in a preferred embodiment of the present invention theelastomer (i) is a block copolymer comprising at least two terminalpoly(monovinylaromatic hydrocarbon) blocks and at least one centralpoly(conjugated diene) block, forming a continuous network.

Preferably the block copolymer of the preferred embodiment is selectedfrom the group consisting of those of formulae A(BA)_(m) or (AB)_(n)X,wherein A represents a block of predominantly poly(monovinylaromatichydrocarbon), wherein B represents a block of predominantlypoly(conjugated diene), wherein X represents the residue of amultivalent coupling agent and wherein n represents an integer≧1,preferably ≧2, and m represents an integer≧1, preferably m is 1.

More preferably the A blocks represent predominantly poly(styrene)blocks and the B blocks represent predominantly poly(butadiene) orpoly(isoprene). Most preferably the B blocks are predominantlypoly(butadiene). Multivalent coupling agents to be used include thosecommonly known in the art. With the term “predominantly” it is meantthat the respective blocks A and B may be mainly derived from monovinylaromatic hydrocarbon monomer and conjugated diene monomer, whichmonomers may be mixed with other structurally related or non-relatedco-monomers, e.g. mono-vinyl aromatic hydrocarbon monomer as maincomponent and small amounts (up to 10%) of other monomers or butadienemixed with isoprene or with small amounts of styrene. More preferablythe copolymers contain pure poly(styrene), pure poly(isoprene) or purepoly(butadiene) blocks.

Preferably the A blocks of the block copolymers have an apparent mol wt.in the range of from 3,000 to 100,000, preferably in the range of from5,000 to 50,000; whilst the B blocks preferably have an apparent mol wt.in the range of from 10,000 to 300,000, more preferably in the range offrom 40,000 to 200,000, and most preferably in the range of from 45,000to 120,000.

The originally prepared poly(conjugated diene) blocks usually contain inthe range of from 5 to 50 mol % of vinyl groups, originating from 1,2polymerisation relative to the conjugated diene molecules, andpreferably a vinyl content in the range of from 10 to 25%.

The block copolymers to be used according to the present inventionpreferably contain polymerised vinyl aromatic monomers in an amount inthe range of from 10 to 60% by weight, more preferably in the range offrom 15 to 45% by weight.

The apparent molecular weight of the total block copolymer willpreferably be in the range of from 50,000 to 600,000 and more preferablyin the range of from 150,000 to 550,000.

The block copolymers may optionally be hydrogenated. The hydrogenationmay be complete or partial and may be achieved, if desired, bytechniques well known in the art.

Preferred elastomers for use in the present invention are available fromKraton B.V. (Kraton is a trademark), for example Kraton D-1184.

The bitumen composition of the present invention comprises a lithiumsalt of a C₁₀-C₄₀ fatty acid or hydroxy fatty acid (iv). Preferably, theamount of lithium salt is from 0.5 to 20% wt, more preferably 1 to 10%wt and most preferably 2 to 6% wt, based on total bitumen composition.

Preferred lithium salts according to the present invention are lithiumsalts of fatty acids or hydroxy fatty acids having 12-22 carbon atoms.Examples of lithium salts which may very conveniently be used includelithium stearate, lithium hydroxystearate, lithium palmitate and lithiumhydroxypalmitate; lithium stearate being particularly preferred. Lithiumsalts of unsaturated fatty acids may also be applied as well as mixturesof various lithium salts of fatty acids or hydroxy fatty acids.

The bitumen composition of the present invention may optionally containone or more fillers (v). The amount of filler may be up to up to 70% wtbased on total composition. Preferably, the amount of filler, whenpresent, is in the range of from 15 to 60% wt, more preferably 25 to 50%wt, based on total composition. The filler may be inorganic or organicin nature. Examples of fillers that may be conveniently used includechalk, limestone, unbaked powdered gypsum, talcum, fly ash, coalcombustion waste, pigments such as titanium dioxide, iron oxide,chromium oxide, diatomaceous earth and other clays, quartz flour,calcium carbonate and fumed silica. A filler which has been found togive very good results in the present invention is calcium carbonatefiller.

For the avoidance of doubt, and as will be readily understood by thoseskilled in the art, in the bitumen composition of the present inventionthe total amount of components (i), (ii), (iii), (iv) and (v) does notexceed 100% wt of the total bitumen composition.

The bitumen composition of the present invention may further compriseadditional additives conventionally used in bituminous adhesives, suchas anti-oxidants, microbicides and water repellents.

The bitumen composition of the present invention may be prepared byvarious methods known to those skilled in the art. However, a preferredmethod of preparing the composition comprises adding the elastomer as asolution in the solvent to a pre-blend of bitumen and lithium salt. Itis preferred to prepare the composition in this way as in order to mixthe bitumen and lithium salt it is often necessary to heat the bitumento high temperature, and this may decompose any elastomer present.However, it can be difficult to mix the elastomer directly into thepre-blend of bitumen and lithium salt, and it is therefore advantageousto dissolve the elastomer in the solvent prior to addition.

Accordingly, the present invention further provides a process ofpreparing a bitumen composition which comprises mixing a first component(A) comprising (i) from 0.1 to 25% wt of an elastomer, and (ii) from 0.1to 40% wt of a solvent; with a second component (B) comprising (iii)from 30 to 99% wt of a bitumen, (iv) from 0.1 to 30% wt of a lithiumsalt of a C₁₀-C₄₀ fatty acid or hydroxy fatty acid, and optionally (v)from 0 to 70% wt of a filler, all weights based on total bitumencomposition, wherein the solvent is of general formula (I)

wherein R¹ represents a hydrogen atom or a hydrocarbyl group having from1 to 6 carbon atoms, R² represents a hydrocarbyl group having from 1 to6 carbon atoms, and the sum of the carbon atoms in R¹ and R² is from 5to 7.

Materials and quantities described hereinabove as being preferred withregard to the bitumen composition of the present invention, aresimilarly preferred with regard to the process of the invention.

Component (A) of the process may be prepared conveniently by dissolvingthe elastomer in the solvent of general formula (I) at ambienttemperature (25° C.). The amount of elastomer to solvent in component(A) may vary, however, component (A) may conveniently comprise from 1 to25% wt, more preferably from 5 to 15% of elastomer, based on total (A)component. Where the bitumen composition comprises additional additivessuch as anti-oxidants or water repellents, these are preferablyincorporated into component (A)

Component (B) is preferably prepared by heating the bitumen to atemperature in the range of from 200 to 300° C., more preferably 220 to280° C., and then adding the lithium salt. The bitumen and lithium saltare then mixed, preferably by a mechanical mixer at a rate of greaterthan 500 rpm, more preferably from 800 rpm to 1200 rpm, until ahomogenous blend is obtained. If required a filler is added to themixture at elevated temperature, preferably of from 200 to 300° C.

Component (A) may be mixed into component (B) at ambient temperature(25° C.), however, if required the (B) component may be heated to atemperature of up to 80° C., preferably from 50 to 80° C. to facilitatemixing. Whilst the relative amount of component (A) to component (B) mayvary, the weight ratio of component (A) to component (B) may beconveniently in the range of from 1:20 to 1:5, more preferably from 1:12to 1:6, based on total amount of (A) and (B).

The bitumen composition of the present invention may be cold-applied andused on a wide variety of substrates, including metal, concrete, woodand felt, even under damp conditions. Accordingly, the present inventionfurther provides for the use of a bitumen composition according to thepresent invention as a cold-applicable adhesive. By ‘cold-applicable’ itis meant that the composition may be applied at ambient temperature (25°C.), without needing to heat the composition.

When used as a cold-applicable adhesive, the composition is especiallyuseful as a joint sealant and for waterproofing concrete surfaces. Whenthe composition is to be applied to a specific area (e.g. when used as ajoint sealant) the composition may be conveniently applied at ambienttemperature by means of a spatula, a hand-held cartridge or any othersuitable application device: where the composition is to be applied overa large surface area, it may conveniently by applied by spray or bybrush. When used in very cold conditions, a minor amount of high-boilingpoint (at least 200° C.) diluent may conveniently be added to thecomposition. Examples of diluents that may be used include aliphatichydrocarbons, ethers, and di- or polyglycols that have a boiling pointof at least 200° C.

The present invention will be further understood from the followingillustrative examples.

EXAMPLES

In the following examples a selection of solvents were tested toevaluate their ability to dissolve elastomer, and the performance ofcold-applicable bituminous adhesives comprising the solvents comparedwith a known composition comprising 1,1,1-trichloroethane.

Solubility Test

A variety of solvents were selected, and their ability to dissolveelastomer assessed by preparing 10% wt solutions of elastomer in eachsolvent. The elastomer employed was a non-hydrogenated radialstyrene-butadiene-styrene block copolymer having an apparent molecularweight of 420,000 and a styrene content of 30% wt. (Kraton D-1184,obtained from Kraton B.V.: ‘Kraton’ is a trade mark).

The results of the tests showed three general solvent behaviours,categorised as:—a) ‘Dissolved’—the elastomer completely dissolved in thesolvent: b) ‘Swelling’—the elastomer swelled to form a gel, and c)‘Scattering’—the elastomer formed a dispersion in the solvent, whichtook on the appearance of a milky liquid (fine scattering) or asuspension of coarse particles (coarse scattering).

The results of the solubility test are shown in Table 1. Where theelastomer dissolved, the time taken for it to dissolve completely isindicated.

The solubility results in Table 1 show that the use of non-aromaticaliphatic hydrocarbon solvents results in an unusable gel, whilsthydroxy functionalised solvents such as ethyl lactate and methylproxitol form dispersions. Other than 1,1,1-trichloroethane, thesolvents which dissolved the elastomer completely were n-butylpropionate, decahydro naphthalene (DHN) and n-propyl bromide. TABLE 1Solvent Solubility Dissolving Time (25° C.) Shellsol D25¹ Swelling NotSoluble Isoparaffin blends² Swelling Not Soluble DHN³ Dissolved 4 hoursn-Butyl Propionate⁴ Dissolved 2 hours Methyl Proxitol⁵ Scattering(coarse) Not Soluble Methyl Proxitol Acetate⁶ Scattering (fine) NotSoluble n-Propyl Bromide⁷ Dissolved 1 hour Ethyl lactate⁸ Scattering(coarse) Not Soluble PGPE⁹ Scattering (fine) Not Soluble1,1,1,-Trichloroethane Dissolved 1 hour¹A low aromatic content hydrocarbon solvent obtained from ShellChemicals (‘Shellsol’ is a trade mark).²A mixture of non-chlorinated hydrocarbon solvents obtained from Dercamunder the trade names ‘Evolve CH 10’, ‘Evolve CH 12’ and ‘Evolve CH 14’(‘Evolve’ is a trade mark)³Decahydro naphthalene (DHN) obtained from Degussa-Huls A.G.⁴EtCO₂Bu - obtained from the Eastman Chemical Company.⁵1-Methoxy-2-propanol (CH₃OCH₂CH(OH)CH₃) obtained from Shell Chemicals.⁶1-Methoxy-2-propanol acetate (CH₃CO₂CH(CH₃)CH₂OCH₃) obtained from ShellChemicals.⁷CH₃CH₂CH₂Br obtained from Dercam.⁸CH₃CH(OH)CO₂Et obtained from the Dow Chemical Company⁹Propylene glycol n-propyl ether (n-PrOCH₂CH(OH)CH₃)(PGPE) obtained fromthe Dow Chemical Company under the trade name Dowanol PNP (‘Dowanol’ isa trade mark)Adhesive Testing

Bitumen compositions were prepared using a variety of solvents and theirperformance as adhesives evaluated.

The bitumen compositions were prepared by manually blending a mixture ofelastomer and solvent (component A) into a pre-prepared mixture ofbitumen, lithium stearate and filler (component B), at a temperature of60° C. The weight ratio of component A to component B was 3:17 (i.e. 15%wt of A, and 85% wt of B).

The B component comprised 48.4% wt of a naphthenic straight run bitumenhaving a penetration at 25° C. from 160 to 220 dmm (measured accordingto EN 1426), 5.6% wt of lithium stearate, and 46.0% wt of a calciumcarbonate filler, all weights based on total B component. The Bcomponent was prepared by heating the bitumen to a temperature ofapproximately 250° C., and then adding the lithium salt and mixing for 1hour with a mechanical mixer at a rate of 1000 rpm. The filler was thenadded at a temperature of 220° C., and the mixture stirred until anhomogenous blend was obtained.

The bitumen compositions were cold applied (25° C.) using a wide spatulato a dry brick surface, a damp brick surface and to a brick surfaceunder water. The adhesive performance of the compositions was assessed,and the curing performance assessed after 1 week under the respectiveconditions.

The results are shown in Table 2. TABLE 2 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6Ex. 1 (comp.) (comp.) (comp.) (comp.) (comp.) Solvent n-Butyl n-PropylDHN Methyl Methyl 1,1,1- Propionate Bromide Proxitol Proxitol AcetateTrichloroethane Adhesion:- Dry surface ++ ++ ++ ++ ++ ++ Damp surface ++− + − + ++ Under water ++ − + −− + ++ Curing:- Dry surface + ++ − + − ++Under water + NT − NT + +Good ++;Medium +;Poor −;Bad −−NT = Not TestedAdhesionGood: Complete adhesion during application.Medium: Some areas of non-adhesion during application.Poor: Predominantly non-adhesion during application.Bad: Complete non-adhesion during application.CuringGood: All solvent evaporated/migrated to leave a hard material.Medium: Most solvent evaporated/migrated but material not yet fullyhard.Poor: Large amount of solvent remains and material still soft.Bad: No curing: the material is largely unchanged from the time ofapplication.

From Table 2 it can be seen that only the composition of Example 1(containing n-butyl propionate) displays good adhesion in allconditions, satisfactory curing, and an overall performance approachingthat of the composition containing 1,1,1-trichlorethane (Example 6).

To compare directly the curing performance of a composition according tothe invention with a composition comprising 1,1,1-trichloroethane assolvent, two further compositions were prepared in an analogous mannerto that described for Examples 1 to 6. The compositions were applied tobricks and curing monitored in dry conditions and under water, includingperiodic weighing of samples to asses solvent loss.

The contents and performance of the compositions are shown in Table 3.In Table 3 the designations Good, Medium, Poor and Bad are as defined inTable 2.

From Table 3 it can be seen that the bitumen composition according tothe present invention (Example 7) displays a curing performanceapproaching that of the composition comprising 1,1,1-trichloroethane(Example 8) under dry conditions, and a superior performance to that ofExample 8 when left to cure under water.

Accordingly, from the illustrative examples described above it can beseen that the bitumen compositions of the present invention are, in allaspects, excellent substitutes to known cold-applicable bituminousadhesives comprising chlorinated solvents. TABLE 3 Example 7 Example 8(comp.) Solvent n-Butyl Propionate 1,1,1-Trichloroethane Acomponent^((i)) % w Solvent 80.3 82.6 % w Kraton D-1184 12.4 10.9 % wInipol 002^((iv)) 7.3 6.5 % w B component^((ii)) 86.3 84.9 % w Acomponent 13.7 15.1 Bitumen Composition^((iii)) % w Solvent 11.0 12.5 %w Kraton D-1184 1.7 1.6 % w Inipol 002 1.0 1.0 % w Bitumen 41.8 41.1 % wLithium Stereate 4.8 4.8 % w Filler 39.7 39.0 Dry Curing 1 week + ++ 2week ++ ++ Under Water Curing 1 week ++ + 1 month ++ ++Good ++;Medium +;Poor −;Bad −−^((i))Based on total weight of A component^((ii))Based on total weight of A + B^((iii))Based on total weight of bitumen composition^((iv))An oleic amine based waster repellant obtained from Ceca.

1. A bitumen composition comprising:— (i) from 0.1 to 25% wt of anelastomer, (ii) from 0.1 to 40% wt of a solvent, (iii) from 30 to 99% wtof a bitumen, (iv) from 0.1 to 30% wt of a lithium salt of a C₁₀-C₄₀fatty acid or hydroxy fatty acid, and optionally (v) from 0 to 70% wt ofa filler, all weights based on total bitumen composition, wherein thesolvent is of general formula (I)

wherein R¹ represents a hydrogen atom or a hydrocarbyl group having from1 to 6 carbon atoms, R² represents a hydrocarbyl group having from 1 to6 carbon atoms, and the sum of the carbon atoms in R¹ and R² is from 5to
 7. 2. The bitumen composition of claim 1, wherein the elastomer is ablock copolymer comprising at least two terminal poly(monovinylaromatichydrocarbon) blocks and at least one central poly(conjugated diene)block.
 3. The bitumen composition of claim 1, wherein, in the solvent ofgeneral formula (I), R¹ and R² each independently represent an alkylgroup having from 2 to 4 carbon atoms and the sum of the carbon atoms inR¹ and R² is
 6. 4. The bitumen composition of claim 3, wherein thesolvent of general formula (I) is n-butyl propionate.
 5. The bitumencomposition of claim 1, wherein the bitumen has a penetration in therange of from 100 to 300 dmm.
 6. The bitumen composition of claim 1,wherein the lithium salt is a lithium salt of a C₁₂-C₂₂ fatty acid orhydroxy fatty acid.
 7. A process comprising using the bitumencomposition of claim 1 as a cold-applicable adhesive.
 8. A process ofpreparing a bitumen composition which comprises mixing a first component(A) comprising (i) from 0.1 to 25% wt of an elastomer, and (ii) from 0.1to 40% wt of a solvent; with a second component (B) comprising (iii)from 30 to 99% wt of a bitumen, (iv) from 0.1 to 30% wt of a lithiumsalt of a C₁₀-C₄₀ fatty acid or hydroxy fatty acid, and optionally (v)from 0 to 70% wt of a filler, all weights based on total bitumencomposition, wherein the solvent is of general formula (I)

wherein R¹ represents a hydrogen atom or a hydrocarbyl group having from1 to 6 carbon atoms, R² represents a hydrocarbyl group having from 1 to6 carbon atoms, and the sum of the carbon atoms in R¹ and R² is from 5to
 7. 9. The process of claim 8 further comprising preparing component(B) by heating the bitumen to a temperature in the range of from 200 to300° C., and then adding the lithium salt.
 10. The process of claim 8,wherein the weight ratio of component (A) to component (B) is in therange of from 1:20 to 1:5.
 11. The bitumen composition of claim 2,wherein, in the solvent of general formula (I), R¹ and R² eachindependently represent an alkyl group having from 2 to 4 carbon atomsand the sum of the carbon atoms in R¹ and R² is
 6. 12. The bitumencomposition of claim 2, wherein the bitumen has a penetration in therange of from 100 to 300 dmm.
 13. The bitumen composition of claim 3,wherein the bitumen has a penetration in the range of from 100 to 300dmm.
 14. The bitumen composition of claim 4, wherein the bitumen has apenetration in the range of from 100 to 300 dmm.
 15. The bitumencomposition of claim 2, wherein the lithium salt is a lithium salt of aC₁₂-C₂₂ fatty acid or hydroxy fatty acid.
 16. The bitumen composition ofclaim 3, wherein the lithium salt is a lithium salt of a C₁₂-C₂₂ fattyacid or hydroxy fatty acid.
 17. The bitumen composition of claim 4,wherein the lithium salt is a lithium salt of a C₁₂-C₂₂ fatty acid orhydroxy fatty acid.
 18. The bitumen composition of claim 5, wherein thelithium salt is a lithium salt of a C₁₂-C₂₂ fatty acid or hydroxy fattyacid.
 19. A process comprising using the bitumen composition of claim 2as a cold-applicable adhesive.
 20. A process comprising using thebitumen composition of claim 3 as a cold-applicable adhesive.
 21. Aprocess comprising using the bitumen composition of claim 4 as acold-applicable adhesive.
 22. A process comprising using the bitumencomposition of claim 5 as a cold-applicable adhesive.
 23. A processcomprising using the bitumen composition of claim 6 as a cold-applicableadhesive.
 24. The process of claim 9, wherein the weight ratio ofcomponent (A) to component (B) is in the range of from 1:20 to 1:5.